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Infinite sensation

11 August 2001

By Alison Motluk

EVERYONE knows there are five basic senses. But try separating them one from the other in your daily life and suddenly they don’t feel so distinct.

Eat a banana, for instance, and try to taste it without smelling it and experiencing that banana-y texture on your tongue. Can you really just taste, or must you sometimes taste-smell-feel? Try talking to your lover. Listen to what is said without watching the mouth move or feeling the caress of a hand. Can you simply hear, or is there always an element of hear-see-touch? Even on the phone, can you hear a voice without imagining a face? Hard, isn’t it?

The prevailing view of the brain still holds that there are five separate senses that feed into five distinct brain regions preordained to handle one and only one sense. The yellowness of the banana skin, the texture of its flesh, its smell and taste-each of these elements is parcelled up and analysed in isolation. Some theories of consciousness suggest that these dedicated brain areas somehow stamp each sense with a unique “feeling”. Then, the theory goes, the brain pastes the fragments back together, calls on memory to give it a name and recall what it’s for and, voila, a banana.

But perhaps it’s time for a radical rethink of how the brain works. Tasks we’ve long assumed were handled by only one sense turn out to be the domain of two or three. And when we are deprived of a sense, the brain responds-in a matter of days or even hours-by reallocating unused capacity and turning the remaining senses to more imaginative use. All this begs …